sut with phono pre, does it keep the pre's signatu

The 834 already has SUT's built in for the MC section, so you would be substituting the Bobs Cinemag SUT for the EAR's.
Whether the Cinemags would be better or not I'm not sure - would probably depend on the cartridge you're using.

FWIW, while I think Bob's Cinemag SUT is a great value, its hardly a giant killer. Compared to the Choir Audio SUT-H7 (using Hashimoto HM7 transformers) the Cinemag sounds less transparent and dynamic, not as finely detailed and has less bass tautness/apparent extension. The H7 is a pretty big step up (sorry for the pun) IMO.
BTW, both the Cinemags and the H7 share esentially the same step up ratios - so its an apples to apples comparison.

I would double check w/ EAR or your dealer to make sure this is OK to do in the first place. I also own the Choir Audio SUT-H7, and agree it is a great sounding unit. I haven't heard the Bob's Cinemag, but it has quite the following. Certainly the H7 should be better at 3X the price. Generally an SUT is used in to a MM input, rather than a MC input. Not sure if your 834P has a MM though. What is the reason you want to try an SUT ?

I am not sure whether or not I am going the SUT direction. It was suggested by the previous owner of the EAR. He said that the MC section is the weak link on this unit. I realize that it will go through the MM but I just didn't know if you only get the tone of the SUT or also the tone the base phono pre you are using with the SUT.

You will get a combination of the two; this is inevitable as no component is totally neutral. This does not mean that it will be worse than the EAR alone; just different. The MC section is often weaker, I used a Bob's with my Musical Fidelity NuVista M3 instead of the built in MC and it was better.